High-Temperature-Gradient Casting of in Situ Multifilamentary Superconductors
The in situ process for Cu-Nb-Sn has been developed on a laboratory scale, and recently several groups have produced multifilamentary wires with overall critical current densities comparable to commercial continuous-fiber multifilamentary materials [1–3]. The mechanical properties of the in situ wires are considerably better than those of the conventional multifilamentary superconducting wires. For practical applications, it is necessary to demonstrate that the in situ process can be adapted to industrial scale. Various scale-up approaches appear to be feasible. To demonstrate the feasibility of scale-up, a casting arrangement for relatively small-diameter (about 1 cm) rods was developed. Although the present arrangement was developed as an inexpensive demonstration model, which utilized relatively low power and available equipment, the results demonstrate it is possible to cast in situ Cu-Nb rods for large-scale production. Relatively small-diameter in situ rods were chosen because good quality control of the alloy fabrication could be achieved on the basis of prior experience with small chill castings (20 to 30 g). This paper reviews the casting arrangement and discusses the effect of filament spacing on the superconducting and mechanical properties of the wire. A brief description of this casting for in situ Cu-Nb-Sn materials is published elsewhere .
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